A floating dock is a platform or ramp supported by pontoons. These are usually joined to the shore with a ramp that rests upon the dock on rollers, to adjust for the vertical movement of the dock. The dock is usually held in place by vertical poles embedded in the soil under the water or by anchored cables. Frequently used in marinas for small boats, this type of dock maintains a fixed vertical relationship to watercraft secured to it, independent of tidal, river, or lake elevation. It is less suited for larger craft as the docks cannot support large structures or cranes. In some regions of the world, a floating dock is called a pontoon.